Detective Inspector Jack Caffery, a senior member of Bristol's elite major crimes investigation unit, is sent to the scene of a violent carjacking episode.

So far, so routine -- but this is a carjacking with a difference because there was a passenger in the jacked car, an innocent 11-year-old girl. Worse still, she hasn't been freed.

Caffery knows in cases like this that the longer the child is missing, the grimmer the likely outcome, and as the hours tick by the carjacker starts taunting the police. Then another car and its child passenger disappear, and Caffery suddenly gets the feeling that his quarry is not only very clever, but also seems to be ahead of the police at every step.

Meanwhile, Sergeant Flea Marley, who runs the Bristol police's underwater search unit, who is hiding a secret Jack is only too aware of, finds herself trapped in a canal tunnel as she searches for the children. To her horror she realises a ruthless killer knows where she is and intends to end her life.